Abstract: A series volume measurement tests, constant water content isotropic consolidation tests, and true triaxial shear tests on intact expansive soils subjected to freeze-thaw cycles at different moisture levels are conducted to investigate the effects of freeze-thaw cycles on the deformation and strength characteristics of expansive soils. The study investigated the effects of freeze-thaw cycles on the volumetric strain, suction, and yield characteristics of expansive soils, and explored the influence of the intermediate principal stress on the strength properties of expansive soils subjected to freeze-thaw cycles. The results indicate that expansive soil with higher moisture content（w0≥23.0%）exhibits “frost heave and thaw shrinkage” behavior, whereas soil with lower moisture content （w0≤19.8%）demonstrates “frost shrinkage and thaw expansion” characteristics. The mechanical parameters of expansive soils (including suction and strength parameters) exhibit a progressive degradation with increasing freeze-thaw cycles. Notably, the most significant deterioration occurs after the first cycle, while the parameters tend to stabilize after 5 cycles. Under varying numbers of freeze-thaw cycles, both the LC and SD yield lines remain nearly parallel, with the SD yield line forming an obtuse angle with the vertical axis. The plastic expansion region of the expansive soil’s microstructure void ratio, enclosed by the LC yield line, SD yield line, and coordinate axes, gradually decreases with increasing freeze-thaw cycles. Both cohesion and internal friction angle follow an exponential decay pattern. Cohesion is significantly influenced by the coupling effect of initial water content and intermediate principal stress parameter, exhibiting faster attenuation and lower residual strength (35%~61%). In contrast, the internal friction angle decreases linearly with an increase in the intermediate principal stress parameter but maintains a higher residual proportion (77%~82%), indicating greater stability. The established quantitative model demonstrates that the strength degradation of soil under freeze-thaw conditions primarily results from the loss of cohesion. The findings provide a theoretical basis for engineering construction and hazard prevention in expansive soil regions subject to seasonal freezing.